In certain applications, such as high-power microwave sources, pulsed lasers, particle beam generators, nuclear event simulators, and directional energy weapons, and the like, it is necessary to store electrical energy for release in pulses having extremely fast rise times (e.g., .ltorsim.10 nanoseconds) and short durations (100 nanoseconds to microseconds).
High current self-sustained diffuse glow discharges are suitable for use in high voltage pulsed power applications where fast closing, high repetition rate switching is required. A schematic showing the operation of a UV light triggered glow discharge closing switch in a capacitive energy storage circuit is shown in FIG. 1. The major problems that have been encountered with this type of switch are the high impedance of the discharge and the instabilty of the glow discharge which leads to the formation of electrical arcs between the switch electrodes and consequently destroys the repetitive operation of the switch. The voltage waveform that appears across the switch electrodes is shown schematically in FIG. 2. The present invention describes gas mixtures which will lower the switch voltage V.sub.s (i.e., increase the switch efficiency) and similarly maintain the discharge at the operating voltage V.sub.s and thereby increasing the stability of the discharge.
It has been found by the present inventors that the physio-electrical properties of the gases used in these switches were leading to the unstable high impedance (low efficiency) glow discharges resulting in poor switching characteristics.
Accordingly, there is need for a gas mixture for use in such switches that not only has the capability for conducting a large amount of energy between the electrodes of a diffuse-discharge switch when the switch is in a conducting mode and which has a high insulating capability when the switch is in a nonconducting mode, but also has the capability of providing stable glow discharges during the switch conduction.
The physio-chemical properties required of the gas mixture to achieve high efficiency, stable, discharge operation were discussed in detail for the first time in S. R. Hunter, L. G. Christophorou, and J. G. Carter, "Gas Engineering Studies for High Pressure Self-Sustained Diffuse Discharge Closing Switches." In Gaseous Dielectrics V Edited by L. G. Christophorou and D. W. Bouldin, Pergamon Press, New York, p. 404 (1987); S. R. Hunter, L. G. Christophorou, J. G. Carter, and P. G. Datskos, "New Concepts for High Current Self-Sustained Diffuse Discharge Closing Switches" to be published in the Proceedings of the 6th IEEE Pulsed Power Conference, Arlington, VA, June 29-July 1, 1987; and S. R. Hunter, J. G. Carter, and L. G. Christophorou, "Electron Transport Studies of the Gaseous Media for Diffuse Discharge Closing Switches," Published in Proceeding of the XVIII International Conference on Phenomena on Ionized Gases, Swansea, United Kingdom, July 13-17, 1987, the disclosures of which are all incorporated herein by reference thereto. The stability of the glow discharge is enhanced by tailoring the electron attachment coefficient (.eta./N) and the ionization coefficient (.alpha./N) of the gas mixture in such a way that the rate of change in the electron production and loss is minimal during small perturbations of the applied electric field beyond the glow discharge operating voltage level V.sub.s.
The invention disclosed in the co-pending application by the same inventors, the disclosure of which is incorporated herein by reference thereto as L. G. Christophorou and S. R. Hunter, "Binary and Ternary Gas Mixtures with Temperature Enhanced Diffuse Glow Discharge Characteristics for Use in Closing Switches", U.S. patent application filed concurrently herewith by the same inventors (DOE No. ESID 368-Z), discusses various gases which exhibit decreasing electron attachment with increasing temperature for increasing the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc.
However, increased efficiency and stability during the diffuse glow discharge is still needed to further enhance the desirable characteristics of this type of switch.